Ion exchange treatment of solutions containing cyanohydrins



Patented Dec. 29, 1953 UNITED STATES OFFICE IONEXCHA'N GE TREAT CONTAINING 0 UPS O'IJUTIONS YANOHYDRINS 5.

Frank. R. Riley, New York. N. Y.',.,as'sig nor. to.

' AmerieancCyanamid CompanynNew York;N. I.

acorporatiunofiMaii-ie,

NO-Drawing; ApplicatiomO'ctoben31;.19503. SerialiNo. 19331121 5.3Claims; CL. .2103-241.

This invention: relates to; the:- ion. exchange treatment of" solutions: containing aldehydezcw anohydrinsa; and/on ketone. cyanohydrinst' and more; particularly/7,2. to the-ion; exchange-treatment ottsolutions containing;lactonitrilee.

According: to? the; present invention: I have found-that: when .an. aqueous solution containing an aldehyde and/or" leetonea cyanohydrin is broughtzirrtoacontact swithra strongly 'basicranion exchange: resin; whiclrcontains:- quat-ernary"-ame monium salts and which hasrbeenzia-ctivatedi alkali? metal. hydroxide; the: anion: exchange resin: performs: two fimctions: It: decomposes the:

acrylonitrile, lactonitrile. and"hydrocyanic acid1' The acrylonit'rile is then separatedlffrom the; solution. by distillation, leaving, an aqueous residue containing lactonitrile.

The presence of -potential hydrogen cyanide or hydrocyanic acid in the: waste efliuent-oiv any commercial-process always presents a serious disposal problem. For instance, in the acrylonitrile process generally outlined above it is not possible to dispose of the waste eifiuent containing lactonitrile by merely running the solution 011 into a natural body of water because there is some free hydrocyanic acid present in the solution. By treating this solution, however, according to my process the harmful hydrocyanic acid which is present in the free state and that which is formed by conversion of the lactonitrile is removed whereupon the remainder of the solution may be readily disposed of.

Moreover, it is an advantage of the process of the present invention that the waste disposal problem can be avoided entirely if the efiiuent from the scrubber is treated directly. In this way the expensive distillation step to separate the desired acrylonitrile from lactonitrile also present in the solution is avoided.

The invention will be described in greater detail in coniunction with the following specific examples which are given for purposes of illustration. It is not intended to limit the scope of the invention to the details of the examples.

2. Example 1 bed. ofanion exchange resin completely act'iVa;1Ied"W ith"3I= 10%" aqueous sodium hydroxide solution: and rinsed free of sodium is set up, and an aqueous infl uent" containing approximately 1500*:part's per million, as HCN, of lactonitrile is run downflow through the-bed at mate of about 1 gauon: per minute per cubic foot. Spot checks are made during the-run todeterm'ine the total HCN (lactonitrile plus HCN) leakage, and the capacity- 0f the' r'esi-n is computed to an endpoint of l'0'p; p.- m".. a'ssHCN', total leakage. Check runs are: then-'m'ade after" regenerating" the resin with 20 lbs. era 10% -solution' of sodium hydroxide per cubic foot ofresin-and rinsing to 0p. pm. sodium leakage: The results of" the initial and subse quent runs-are as follows? og aqit es 5 Average 011'" Run. Regeneration. i 10 leakagdl-p. p. m. p; m. i totalHON 1; Complete activation; Less than 0.1.... 10. 5 2 .2Qlbs.-NaOH/cu.it..-- .do.- 10.8 3'' I 201bsrNa'0H/ohxfif; ..d'o 10. 8

His note'd thattheresin' turns dark, the color change appearing first at'the. bottom of the resin column andviorking its way up through the resin until "after two" runs theu'esin is'comple'tel'y dark'in color: This color changeis apparently due toa'rea'ction' betweentheresin and: the acet-' aldehyde liberated during the run but is accom panied by no loss in capacity or physical failure of the resin.

Example 2 The distillation efiluent from an acrylonitrile process which contains a total of 509 p. p. m., as HCN, of HCN (lactonitrile plus HCN) including 54 p. p. m. of free HCN are subjected to the same treatment as described in Example 1 starting with new, completely activated, rinsed resin. The results follow:

A completely activated and rinsed bed of resin is set up as in Example 1. An aqueous solution containing from about 2-3% acrylonitrile, and a total of 422 p. p. m., as HCN, of l-ICN (lactonitrile plus HCN) including 24 p. p. m. of free l-ICN is run downfiow through the bed in accordance with the procedure of Example 1. Throughout the run the leakage of total HCN remains below 0.1 p. p. m. as HCN, and the resin has a capacity to p. p. m. total HCN of 10.2 kilograins per cubic foot of resin.

The anion exchange resin used in Examples 1-3 is one known as Dowex-Z and believed to be a styrene based copolymer type resin containing quaternary ammonium groups. Similar resins known as Amberlite IRA 409 and Amberlite IRA 4210 may be substituted as may other strongly basic anion exchange resin containing quaternary ammonium groups such as, for example, the epichlorohydrin-polyalkylene polyamine condensation products of U. S. Patent No. 2,469,683 and application Serial No. 102,949 filed July 2, 1%9, etc.

The resins are activated in the usual manner by treatment with a solution of an alkali metal hydroxide such as sodium hydroxide or potassium hydroxide. Since extreme basicity of the resin is necessary for removal of weak hydrocyanic acid, activation with a weaker alkali such as the alkali metal carbonates, i. e., sodium oarbonate, potassium carbonate, will generally not be sufiicient.

My process is applicable to the ion exchange treatment of any cyanohydrin formed by reaction of an aldehyde or a ketone with hydrogen cyanide. Thus, I contemplate treatment of the cyanohydrins of aliphatic and aromatic aldehydes, of aliphatic ketones and of mixed aliphatic-aromatic ketones such as the cyanohydrins of propionaldehyde, benzaldehyde, acetone, methyl ethyl ketone, methyl vinyl ketone, benzyl methyl ketone, phenyl ethyl ketone, and the like. However, the solutions to which the process of the present invention is particularly applicable, i. e., those produced in the manufacture of acrylonitrile, contain lactonitrile. These solutions generally contain no more than about 0.15% by weight of total HON which includes free hydrocyanic acid and hydrocyanic acid produced upon decomposition of the lactonitrile. If acrylonitrile is present, it is generally present in small quantities of the order of about 2-3%.

It is an advantage or the present invention that the anion exchanger acts in a dual capacity. It

not only removes free hydrocyanic acid present in a given solution but it also decomposes cyanohydrin there present to its components, carbonyl compound and hydrocyanic acid, and then removes the hydrocyanic acid so formed.

I claim:

1. A process which comprises passing an aqueous solution containing a cyanohydrin of the group consisting of aldehyde cyanohydrins and ketone cyanohydrins through, and in contact with, a bed of a strongly basic anion exchange resin containing quaternary ammonium groups, said resin being activated by treatment with an aqueous solution of an alkali metal hydroxide, whereby said cyanohydrin is decomposed to its component parts, carbonyl compound and hydrocyanic acid, and substantially all hydrocyanic acid is removed from said solution.

2. A process which comprises passing an aqueous solution containing lactonitrile through, and in contact with, a bed of a strongly basic anion exchange resin containing quaternary ammonium groups, said resin being activated by treatment with an aqueous solution of an alkali metal hydroxide, whereby said lactonitrile is decomposed to its component parts, acetaldehyde and hydrocyanic acid, and substantially all hydrocyanic acid is removed from said solution.

3. A process according to claim 2 wherein the solution containing lactonitrile also contains some free hydrocyanic acid.

4. A process according to claim 2 wherein the solution containing lactonitrile also contains acrylonitrile.

5. A process according to claim 2 wherein the solution containing lactonitrile contains no more than about 0.15% by weight total HCN, including any hydrocyanic acid present in the free state and any hydrocyanic acid to be derived from the lactonitrile, and about 2-3% acrylonitrile.

FRANK R. RILEY.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 2,228,514 Griessbach et al. Jan. 1 1941 2,469,693 Lundberg May 10, 1949 2,543,666 Michael Feb. 27, 1951 FOREIGN PATENTS Number Country Date 592,767 Great Britain Sept. 29, 1947 

1. A PROCESS WHICH COMPRISES PASSING AN AQUEOUS SOLUTION CONTAINING A CYANOHYDRIN OF THE GROUP CONSISTING OF ALDEHYDE CYANOHYDRINS AND KETONE CYANOHYDRINS THROUGH, AND IN CONTACT WITH, A BED OF A STRONGLY BASIC ANION EXCHANGE RESIN CONTAINING QUATERNARY AMMONIUM GROUPS, SAID RESIN BEING ACTIVATED BY TREATMENT WITH AN AQUEOUS SOLUTION OF AN ALKALI METAL HYDROXIDE, WHEREBY SAID CYANOHYDRIN IS DECOMPOSED TO ITS COMPONENT PARTS, CARBONYL COMPOUND AND HYDROCYANIC ACID, AND SUBSTANTIALLY ALL HYDROCYANIC ACID IS REMOVED FROM SAID SOLUTION. 